In diagnosing and treating diseases of various body cavities and organs, it is necessary to deliver diagnostic and/or therapeutic agents to the organs at specified locations. Most common routes of drug delivery include a non-invasive peroral (through the mouth), topical (skin), transmucosal (nasal, buccal/sublingual, vaginal, ocular and rectal) and inhalation routes. However, many therapeutic and diagnostic agents in general may not be delivered using these routes because they might be susceptible to enzymatic degradation or cannot be absorbed into the systemic circulation efficiently due to molecular size and charge issues, and thus, will not be therapeutically effective. For this reason, many such drugs have to be delivered by injection.
There are several known problems associated with the injection process. One of such problems is undesirable extravasation of the diagnostic or therapeutic agents into tissue, which is particularly prevalent with intravenously injected agents. Extravasation generally refers to leakage of fluids out of a container, and more specifically refers to leakage of intravenous drugs from a vein into surrounding tissues, resulting in an injury to the tissues. Once the intravenous extravasation has occurred, damage can continue for months and involve nerves, tendons and joints. If treatment is delayed, surgical debridement, skin grafting, and even amputation have been known to be the unfortunate consequences.
Occurrence of extravasation is possible with all intravenuous drugs, but it is a particularly significant problem with cytoxic drugs used for treatment of cancer (i.e. during chemotherapy).
Chemotherapy is the general term for any treatment involving the use of chemical agents to stop cancer cells from growing. Chemotherapy can eliminate cancer cells at sites great distances from the original cancer. As a result, chemotherapy is considered a systemic treatment. More than half of all people diagnosed with cancer receive chemotherapy. A chemotherapy regimen (a treatment plan and schedule) usually includes drugs to fight cancer plus drugs to help support completion of the cancer treatment.
Chemotherapy can be administered through a vein, injected into a body cavity, or delivered orally in the form of a pill, depending on which drug is used. Chemotherapy works by destroying cancer cells. Unfortunately, it cannot tell the difference between a cancer cell and some healthy cells. Thus, chemotherapy often eliminates not only the fast-growing cancer cells, but also other fast-growing cells in the body, including hair and blood cells. Some cancer cells grow slowly while others grow rapidly. As a result, different types of chemotherapy drugs target the growth patterns of specific types of cancer cells.
Each chemotherapy drug works differently and is effective at a specific time in a life cycle of the cell it targets. Brachytherapy, sometimes called seed implantation, is an outpatient procedure used in the treatment of different kinds of cancer. The radioactive “seeds” are carefully placed inside of the cancerous tissue and positioned in a manner that will attack the cancer most efficiently. The radioactive seeds are about the size of a grain of rice, and give off radiation that travels only a few millimeters to kill nearby cancer cells. There are two different kinds of brachytherapy: permanent, when the seeds remain inside the body, and temporary, when the seeds are inside of the body and are then removed. With permanent implants (e.g. prostate), the radioactivity of the seeds typically decays with time.
The other type of chemotherapy is when cytotoxic agents are delivered intravenously. Veins of people receiving chemotherapy are often fragile, mobile, and difficult to cannulate. Patients who receive chemotherapy at the same site as radiotherapy may experience a reactivation of skin toxicity known as a “recall” phenomenon. Patients who have had previous radiation therapy at the site of injection may develop severe local reactions from cytotoxic drugs. Cytotoxic drugs also have the potential to cause cutaneous abnormalities in areas that have been damaged previously by radiation, even in areas that are distant from the injection site. Patients who receive further chemotherapy in a different site may experience an exacerbation of tissue damage in the original site.
Furthermore, areas of previous surgery where the underlying tissue is likely to be fibrosed and toughened dramatically present an increased risk of extravasation. Radical mastectomy, axillary surgery or lymph node dissection may impair circulation in a particular limb. This reduces venous flow and may allow intravenous solutions to pool and leak around the site of cannulation.
Some chemotherapy drugs often never reach the tumors they are intended to treat because the blood vessels feeding the tumors are abnormal. A tumor's capillaries (small blood vessels that directly deliver oxygen and nutrients to cancer cells) can be irregularly shaped, being excessively thin in some areas and forming thick, snarly clumps in others. These malformations create a turbulent, uneven blood flow, so that too much blood goes to one region of the tumor, and too little to another. In addition, the capillary endothelial cells lining the inner surface of tumor capillaries, normally a smooth, tightly-packed sheet, have gaps between them, causing vessel leakiness.
The systemic and intravenous side effects of chemotherapy coupled with the limited effect of systemic administration due to abnormal characteristics of tumor blood vessels have given the scientific community pause, in searching for more direct, localized and biologic solutions. Accordingly, the oncology literature has become increasingly populated with articles espousing prospective benefits and positive outcomes of intra-tumoral chemotherapy. A direct administration of cytotoxic drugs such as Mytomycin, Mytomycin-C, Bleomycin, Fluorouracil, Mitoxantrone, Cisplatin, and Avastin in endobronchial intra-tumoral chemotherapy has been done experimentally via direct injection of the agent into the endobronchial tumor. In these cases, the tumor was reported to have died and been subsequently removed.
However, while some experimental uses of the localized delivery of cytotoxic drugs have been attempted, there has been little implementation of such drug delivery in practice, possibly due to numerous problems associated with such delivery. First, it is often necessary to deliver cytotoxic drugs to remote and not easily accessible blood vessels and other lumens within body organs, such as lungs. It is also important to be able to deliver defined doses of the cytotoxic substances because such substances are often very expensive or are capable of causing serious harm if delivered in excess. Moreover, the existing methods lack the ability to contain the cytotoxic agent and/or radiation therapy and mitigate collateral damage to non-affected anatomy and structures.
Several devices have been proposed for a targeted delivery of drugs to internal bodily cavities, such as those disclosed in U.S. Pat. No. 4,994,033 to Shokey et al and U.S. Pat. No. 5,049,132 to Shaffer et al. In these systems, a catheter is provided with an inner balloon and an outer balloon. The inner balloon is inflated to dilate a lesion in an affected blood vessel. The outer balloon is provided with openings, and the drug is ejected out of the openings and into the lesion as the inner balloon is inflated.
While useful for treatment of stenotic lesions, these systems are not particularly useful for other applications, such as treatment of cancerous tumors, and are not efficient at infusing the relevant biological material with the drug. Instead, the catheter may need to remain in place for an unnecessarily long period of time while the infusion of the drug into the biological material is allowed to take place. This is undesirable, especially in applications such as pulmonology, where the patient's respiratory passage has been somewhat restricted by the device. Further, this can result in some of the agent never being infused into the targeted material and instead remaining in the cavity and, after the balloon catheter is removed, subsequently migrating to other undesired portions of the body.
What is desired, therefore, is a balloon catheter system for delivering therapeutic and/or diagnostic agents to bodily tissues, tumors, and other biological materials that can locally deliver the agent to a specific target site. What is further desired is a balloon catheter system for delivering therapeutic and/or diagnostic agents that facilitates the infusion of the drug into surrounding bodily tissues, tumors, and other biological materials. What is also desired is a balloon catheter system for delivering therapeutic and/or diagnostic agents that can adjust for changing conditions during the process of delivering the drug.